There's a good chance that your next Rails job will involve working with an existing application. Here's how I've recently gone about learning several new-to-me codebases.
(May 11, 2020)
Notes on using tests to learn about legacy software.
(April 16, 2013)
Notes from the field as bring a long-neglected Rails application up to speed.
(March 21, 2013)
What do you do if your legacy data defies convention or is just generally complex? Here are some notes from my recent experience using rake to accomplish difficult data migrations.
(December 11, 2011)
Get legacy data? Trucker makes moving it from old codebases into new Rails apps with relative ease.
(September 16, 2011)